Most rain gauges just use a graduated cylinder to capture water as it falls from the sky. That will give you a reasonably accurate measure of how much it rained, but it tells you nothing about how hard it rained. The measurement made here is based on sound. The harder it rains, the lounder the sound will be from water hitting an up-turned metal bowl. The unit above turns the system on when water bridges the traces, then a microphone is used to monitor the sound from the bowl. This is visualized by a VU-meter chip on a column of LEDs mounted inside the house.

After the break you can see the project box that houses the status display. We say it’s too small an needs to be replaced with a much larger LED meter.

The latest Inventgeek project is a 12 outlet control box. They decided to demo it using a giant bulb based VU meter. The control box has 12 individual outlets hooked up to two layers of six solid state relays. [Jared] notes that SSRs can be very expensive, but he purchased his on eBay for ~$10 each. Wiring and installation on this project is incredibly clean and they plan on using the control box for future how-tos. The simple audio circuit used for the VU is based on the LM3915. You’ll find full plans on the site or you can watch the overview video embedded below.

You’ll need either an LM3915 or LM3916 chip, a couple of bread boards, two audio jacks, ten LEDs, and a few other components. Wire them all together per the schematic, then plug an audio source into the input jack. You can plug your speakers or output device into the output jack, and you’re done. Keep in mind that LM3916s switch negative, so positive to positive wiring from LEDs to the bread board will be necessary. The wiring on [Joe]’s version is a bit convoluted, but it can be cleaned up on yours if you take the time. Video embedded below.

This VU meter project by [Daniel Naito] is a great piece of Russian electrocouture. It’s made up of 14 Nixie tubes that display seven frequency bands for the two audio channels. He found this similar project, but wanted to keep the cost low by avoiding such exotic ICs. First, the two input channels are amplified and then split using seven bandpass filters covering 60, 150, 400, 1000, 2500, 6000, and 15000Hz. Then, the AC audio is converted to DC. The final stage converts the logarithmic scale to a linear output. Besides the semirare Nixie tubes, the majority of the parts are just cheap opamps and comparators. The post is an excellent read and you can see it in action in the video below.